\documentclass[border=5pt]{standalone}
\usepackage{
    tikz, % 绘图
    xcolor, % 颜色包
}
\usetikzlibrary{
    arrows, % 箭头形状
    arrows.meta, % 箭头形状
    calc, % 坐标计算
    positioning, % Node位置
    scopes,
    shapes,
    shadows,
}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\definecolor{FC}{rgb}{0, 0, 0.8}

\begin{document}
\begin{tikzpicture}[
    scale=1,
    base/.style={draw=black, fill=FC, line width=1pt},
    ]

\coordinate (O) at (0, 0);
\draw [base, radius=3] (O) circle;

\end{tikzpicture}
\end{document}
